A synchronization mechanism for coordinating tasks even when data accesses are not involved. A barrier is analogous to a gate. Processors or threads operating in parallel reach the gate at different times, but none can pass through until all processors reach the gate. For example, suppose at the end of each day, all bank tellers are required to tally the amount of money that was deposited, and the amount that was withdrawn. These totals are then reported to the bank vice president, who must check the grand totals to verify debits equal credits. The tellers operate at their own speeds; that is, they finish totaling their transactions at different times. The barrier mechanism prevents tellers from leaving for home before the grand total is checked. If debits do not equal credits, all tellers must return to their desks to find the error. The barrier is removed after the vice president obtains a satisfactory grand total.